LOW BACK PAIN
Nothing is more challenging to diagnose than a case of low back pain.
That is why it is so important to have an extensive list of causes in mind
before approaching the patient. Anatomy forms the basis for
developing such a list (Table 45).
Moving posteriorly from the skin inward, one encounters the muscle and
fascial planes, the lumbosacral spine and its ligaments, the spinal cord and
cauda equina, the abdominal aorta and its branches, the rectum, and prostate
in the male, the uterus and pelvic organs in the female, and finally the
bladder.
The skin may be involved by a pilonidal cyst, contusions and
lacerations, or herpes zoster. The muscle and fascia are
involved by fibromyositis, trichinosis, contusions, lacerations, strains,
sprains, and herniation of fat through the subfascial plain. (The latter has
been espoused as a common cause of lumbago.) A more important cause of
muscle spasms and irritation is faulty posture. Slumping over a typewriter
or computer, wearing the wrong shoes (e.g., very high heels),
or having one leg shorter than the other may
cause this.
The next layer is the lumbosacral spine. Vascular lesions are
infrequent here, but inflammation caused by osteomyelitis and tuberculosis
(Pott disease) is still seen in some countries. More common lesions of the
spine inducing low back pain are metastatic carcinoma, herniated discs,
rheumatoid spondylitis, or lumbar spondylosis (often erroneously labeled
osteoarthritis). Osteoarthritis and other arthridites may involve the facets
of the zygapophyseal joints, and produce back pain (“facet syndrome”).
Advanced osteoarthritis leads to spinal stenosis, especially in elderly
persons. Multiple myeloma is not an uncommon cause and should be looked for
in each case. Fractures are particularly frequent in association with this
disease. Fractures are also seen with osteoporosis, osteitis fibrosa
cystica, and osteomalacia. Paget disease, gout, and sprung back (in which
the interspinous ligament is torn) are less common causes of low back pain
originating in the spine. Congenital anomalies such as spondylolisthesis and
scoliosis are important causes. In the spinal cord arteriovenous
anomalies, myelitis, epidural abscesses, and primary tumors are important
causes.
Moving deeper one encounters the aorta, and arteriosclerotic and dissecting
aneurysms come to mind. Disease of the rectum may refer pain to the
low back, particularly hemorrhoids, fissures, perirectal abscesses, and
carcinomas. In the prostate, prostatitis and prostate carcinoma are
frequent causes. Prostate carcinoma, however, produces low back pain most
frequently by metastasis. The bladder and urethra are
infrequent causes of low back pain, but a urinalysis and culture may be
necessary to rule out infections.
To diagnose low back pain in women, the uterus and other
pelvic organs must be examined. Dysmenorrhea (functional) is often
the cause, but tubo-ovarian abscess, ovarian cysts, endometriosis, fibroids,
retroversion or flexion of the uterus, and uterine carcinomas must be looked
for.
Approach to the Diagnosis
Our first priority in a patient who presents with low back pain is to
rule out anything serious such as a herniated disc or cauda equina tumor. A
pelvic and rectal examination must be performed to exclude a pelvic tumor or
prostate carcinoma. A careful neurologic examination must be done. If one is
too busy to do that, referral to an orthopedic surgeon or neurologist is
indicated. The neurologic examination should include an SLR test, femoral
stretch test, careful sensory examination, and an assessment for asymmetric
reflexes. It is wise to carefully measure the thighs and calves to reveal
muscular atrophy. Any findings to support a diagnosis of radiculopathy are a
reasonable indication for a CT scan or MRI of the lumbar spine. However, it
may be wise to have a neurologist or neurosurgeon examine the patient first
because these tests are expensive.
If the patient has normal neurologic, pelvic, and rectal examinations, it is
perfectly legitimate to manage the patient conservatively for a while
without any testing other than clinical. Close follow-up is important in
these cases, however. Should the pain persist despite rest and conservative
treatment, a more thorough diagnostic workup is indicated regardless of the
lack of objective findings. This will include plain films or CT scan and an
arthritis panel.
Other Useful Tests
-
CBC
- Urinalysis (pyelonephritis)
- Urine for Bence–Jones protein (multiple myeloma)
- Protein electrophoresis (multiple myeloma)
- Chemistry panel (metastatic carcinoma)
- Prostate-specific antigen (PSA) (prostatic carcinoma)
- Urine culture and colony count (pyelonephritis)
- Intravenous pyelogram (IVP) (renal calculus, carcinoma)
- Aortogram (abdominal aneurysm)
- Nerve blocks (radiculopathy)
- Lidocaine infiltration of trigger points
- Bone scan (rheumatoid spondylitis)
- Human leukocyte antigen (HLA)-B27 antigen (rheumatoid
spondylitis)
- EMG and NCV (radiculopathy)
- Myelogram (herniated disc, neoplasm)
- Plain films of the lumbar spine
- Sedimentation rate (polymyalgia rheumatica)
- Bone densiometry (osteoporosis)
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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- "The Diagnostic Approach to Symptoms and Signs in Pediatrics" (2006)
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- "Nursing: Interpreting Signs and Symptoms" (2007)
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Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2008 Williams & Wilkins.
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